Because of their toughness and hydrophobic nature, polyolefin resins, such as polyethylene homopolymers and copolymers, are employed in a variety of multilayer film systems and laminations. Nylon, for example, having good oxygen barrier properties, is laminated to a low density polyethylene homopolymer creating a water/oxygen barrier multilayer film system used in food packaging operations. Similarly, aluminum is laminated to low density polyethylene homopolymers to create a flexible metallic film with water/oxygen barrier properties suitable for flexible packaging.
In these laminates, the polyolefin resin is usually adhered to the other layer or substrate through use of an intermediate glue layer. While these glue layer systems initially provide adequate adhesion, they are often severely water sensitive, delaminating quickly if utilized in a water or moisture-containing environment. To ensure long-term, adequate adhesion requires additional processing of the laminate invariably causing increase in cost of the resultant composite system.
It would be desirable then to find a material which could be added to the polyolefin resin which increases the resin's adhesion to various substrates, thus reducing or eliminating the need for an intermediate glue layer and/or costly processing of the laminate to promote adhesion.